More than 40 people were injured in the explosion
The cost of the explosion and fire at the Buncefield oil depot could reach £1 billion, according to a final report by the Major Incident Investigation Board.
The report was published on the third anniversary of the blast at the depot near Hemel Hempstead, Hertfordshire, which injured 43 people.
It was caused by an overflowing fuel storage tank at the depot.
The report said much of the expected costs were made up of compensation claims against the site operators.
Earlier this month, it was announced that five companies would be be prosecuted over the incident, which forced 2,000 people to leave their homes.
The Major Incident Investigation Board (MIIB) chairman, Lord Newton of Braintree, said the final report brought together 78 recommendations.
He said: "This includes some new elements, for example information on economic impact and the mechanism that produced such a severe explosion at Buncefield."
Lord Newton said the decision to prosecute the five companies over the incident was "an important milestone".
Health and Safety Executive chairwoman Judith Hackitt welcomed the report and said: "The work of the MIIB has already had a major impact on the way safety and environmental risks are controlled at similar sites and in ensuring improved resilience."
The Environment Agency said earlier this month that criminal proceedings had now started against Total UK, Hertfordshire Oil Storage and the British Pipeline Agency.
TAV Engineering and Motherwell Control Systems 2003 are also being prosecuted.
The case is due to begin on 23 January at West Hertfordshire Magistrates' Court in Watford.